Heretofore it has been known to use coaxially mounted hollow tubes in the performance of arthroscopic knee surgery. Side cutting is effected by providing co-acting side edges of the tubes which diverge as cutting proceeds in the proximal direction. The outer tube is stationary and is provided with a side port which is opened and closed on each cycle by the inner rotating tube. Vacuum is used to remove the severed body tissue which is sequentially admitted through the port in the outer tube and then withdrawn through the inner tube. U.S. Pat. No. 4,203,444 to Bonnell et al and U.S. Pat. No. 4,274,414 to Johnson et al are examples of the previously described prior art.
These two patents are deficient in a number of respects. First of all, because the blades are made from tubular members, radial deflection is a critical problem. Bonnell et al acknowledges that even slight deflection, even on the order of one or two thousandths of an inch, of the rotating blade radially relative to the stationary blade can result in jamming of tissues cut from the knee. Secondly, neither of the devices in these two patents are useful in cutting straight ahead, i.e., to give an axial bore cut. Both patents are used for side cutting only. Thirdly, because of the manner in which tissue is introduced into the cutters in these patents, namely, by opening and closing a port in the side of a tube, the speed of cutting is much too slow. In U.S. Pat. No. 4,203,444 to Bonnell rotational speeds are limited to 200 rpm or below.